1. Field of the Invention
The present invention relates to lenses for warning and signal lights and more particularly to lenses for redistribution of light from several light sources over the surface area of a signal or warning light
2. Description of the Related Art
Relatively recent advances in the manufacture of light emitting diodes (LEDs) have made them an attractive light source for many purposes previously employing incandescent, halogen or strobe light sources. LED light sources have longer life, higher efficiency and are more durable than previous light sources. One complicating factor in the employment of LED light sources for many purposes is that the light output from several LEDs must be combined to equal the effective light output of a single light source of the type previously used.
It is known to use external lenses configured to refract light emitted from LED light sources into a desired pattern where the light from each LED is redirected to overlap with that of other LEDs in the array to form a desired pattern. Another approach is to fill the surface area for a warning or indicator light with a plurality of outward-facing LEDs. This approach effectively fills the surface area of the warning or indicator light with a relatively uniform light output. Using many LEDs partially defeats the efficiency advantages of an LED by employing more LEDs than would be necessary if the LEDs"" light output were more effectively harnessed. Using many LEDs also complicates design of the light by employing a dense array of LEDs in which heat removal becomes an issue.
An alternative approach is to use a reflector to combine and redirect the light output of a plurality of LEDs. Combining the light output of a plurality of LEDs in a reflector is effective for many warning and signaling purposes. However, there are warning and signal light applications in which the configuration of the necessary warning or indicating light and/or its mounting location is not conducive to use of a reflector.
There is a need in the art for novel and versatile means for redistributing the light from a plurality of LEDs to provide a more uniform fill over the surface area of a warning or signaling light. Uniform light emission may be required comply with standards imposed by governmental agencies for particular warning or signaling purposes. Improved uniformity of light emission may also be desirable for aesthetic purposes.
Briefly stated, a first exemplary embodiment of the present invention comprises a lens member that uses internal reflection to redistribute light from an array of LEDs into a more uniform pattern of light emission. The lens includes collimators positioned to receive the divergent light produced by each LED and redirect that divergent light into a substantially collimated beam. An exemplary embodiment of the collimator is a cone-like configuration of refractive plastic that produces a circular collimated beam which is symmetrically distributed around and parallel to the optical axis of each LED light source.
According to a further aspect of the invention, a first group of internal lens surfaces are arranged to reflect a portion of each collimated beam toward an area of the light assembly which does not include an LED light source and would otherwise present an area of reduced light output. This first group of internal lens surfaces has an angular orientation relative to the collimated beam calculated to redirect the reflected light to a path substantially perpendicular to the optical axis of the LED. The internal lens surfaces are also configured to impart a directional component to the intercepted light in a plane substantially perpendicular to the optical axis of the LED such that the intercepted light is directed toward an area of the warning or signal light lacking a light source. The shape and angular orientation of the first group of internal lens surfaces are dependent upon the distribution of LEDs in the array as well as the overall shape of the warning or signal light.
In accordance with a further aspect of the present invention, a second group of internal lens surfaces is positioned to redirect light from the first group of internal lens surfaces into a path substantially parallel to the path of the LED optical axis/collimated beam. The angular orientation and shape of this second group of internal lens surfaces is related to the shape of the warning or signal light and cooperates with the shape and orientation of the first group of internal lens surfaces. A portion of the light output of each LED light source is redistributed from a collimated beam immediately surrounding the optical axis of the LED to an area of the light assembly that would otherwise present an area of reduced light emission. Areas of reduced light emission, or dark spots, aside from being aesthetically unattractive, may not be permitted by the applicable standard regulating warning and signal lights.
An object of the present invention is to provide a new and improved means for redistributing the light output from a plurality of LEDs over the surface area of a warning or indicating light.
Another object of the present invention is to provide a new and improved method for redistributing light from a plurality of LEDs over the surface area of a warning or signaling light that improves the efficiency and versatility of light sources employing the lens.